Separation of only a specific substance (specimen) from a sample test material containing a plurality of substances is required in various fields. However, in particular, when the presence rate of the specific substrate is low, it is difficult to detect only the specific substance from the sample test material containing the other substances.
One example of a conventional filter device is manufactured by the following process. The surface of the first substrate made of quartz is subjected to chemical treatment such as dry etching or wet etching, or the process treatment by energy ray irradiation treatment with laser, ion beam, or the like, so that a plurality of island-shaped columnar products are formed. Thereafter, a second substrate is joined to the columnar products so as to seal the columnar products. Thus, a space in the island-shaped columnar product sealed by the first substrate and the second substrate is used as a filter flow passage.
Furthermore, in another example of the conventional filter device, a device includes a flow channel on a surface of a first substrate in which a plurality of fibrous layers including fibrous protruding portions are provided in the flow channel and extend to opening portions.
One exemplary use of such a filter device is filtration of leukocyte from erythrocyte in blood. The erythrocyte has the diameter from 7 μm to 8 μm, and can enter and pass through a capillary blood vessel whose diameter is not larger than a half of the diameter of the erythrocyte itself. The leukocyte has a spherical shape whose diameter is from 6 μm to 30 μm, and has smaller deformation ability than flat-shaped erythrocyte. Thus, when the pore size of a filter device is from 3 μm to 6 μm, only the erythrocyte can be allowed to pass.
As one example of a filter device for blood filtration, a leukocyte removing material was disclosed. The leukocyte removing material includes not less than 0.5 wt % and less than 50 wt % of ultra fine fibers whose fiber diameter is not less than 0.02 μm and less than 0.8 μm in which the ultra fine fibers form a mesh structure having circularity of not more than 1.7 and a converted diameter of a circle of not less than 1 μm and less than 20 μm.
Furthermore, in another leukocyte removing device, the leukocyte removing material includes not less than 5 wt % and less than 20 wt % of ultra fine fibers whose fiber diameter is not less than 0.1 μm and less than 0.6 μm in which the ultra fine fiber has a curvature of not less than 1.2.
However, in particular, it is difficult to extract only a specified specimen from a small amount of solution containing many substances.